12Vdc to 220Vac 50W Converter

 In a lot of cases we needed a 220VAC voltage, in sPACes where it does not exist, in order to we supply with power, various small appliances. In the Fig.1, exist a voltage converter circuit from 12VDC in 220VAC, with output power roughly 50W. The circuit is constituted by the oscillator, round the IC1, one divader IC2, one unstable multivibrator IC3, which give in the output symmetrical square signal of Frequency 50Hz, follow a buffer stage with Fet Q1-2, the drive stage Q3-4 and the power stage Q4-5, the power transistors Q5-6, should they are placed in heatsink.. The diodes Zener D2-3, protect the power transistors from voltage peaks, that are produced by the transformer T1. Transformer T1 are a simple power transformer, with intermediate reception, which is connected in the contacts of CO1. For the use that him we want, the T1, is placed in reverse, with secondary convolution it is used as primary, with the intermediate reception she is connected in the positive point of battery 12V and the two other contacts are connected in the EMItters of Q5-6, that are connected in the potential of ground aLTErnately, depending on the rythm that determine outputs 10 and the 11 from IC3.. With this way while in being primary flow AC current, in secondary is created 220V AC square voltage. The use of Crystalic oscillator ensures very good reference frequency 50HZ, and use a simple crystal (CR1). For bigger precision, parallel with the C1, exist a variable capacitor Cx, that ensure the regulation of frequency, so that we take in point P1, frequency 204.8 KHZ. It’s obvious that the output voltage in void of load is bigger than the voltage with load. Also the output voltage depend from the output voltage of battery. Thus for battery voltage 14V, the output voltage is increased at 10%, compared to the battery voltage 12V. If the converter work in load power 40 until 60W, then it CAN be used transformer 2X9V. Various prices of output, for battery voltage 12V and transformer 2X10V, we see in table 1. Elektor6/89

Table 1

Output Power

Output Voltage AC

0W 238V 25W 220V 40W 202V 75W 170V 100W 150V

Part List

R1=10Mohms C4=10uF 16V IC2=4013 R2=100ohms C5=47uF 16V IC3=4047 R3=1.2Kohms C6=470nF 400V CR1=3.2768 MHZ crystal R4=560Kohms D1=5V6 0.4W T1=220Vac/2X10V 2X2.2A *see text R5-6=2.2Kohms D2-3=47V 1W F1=5A Fuse R7-8=56 ohms 5W Q1-2=BS170 F2=0.25A Fuse CX=22pF trimmed capacitor Q3-4=BD139 L1=1H smoothing choke C1-2=22pF ceramic Q5-6=BD249 C3=8.2nF 100V MKT IC1=4060

Fig.2- 12Vdc to 220Vac converter PCB component (top) side.

Fig.3- 12Vdc to 220Vac converter PCB bottom side.

In the Fig.2, exist the printed circuit with the layout of material [ top side ] and in the Fig.3 exist PCB from the bottom side (brass side).

Sam EleCTRonic Circuits 4/02

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